On two recent occasions we had client’s using MS Outlook report that their IMAP settings were not working correctly. This proved to be a challenging issue, as everything they had in their settings appeared to be correct. In addition, their IT Support could not identify the problem. Although everything was in place and tests showed successful completion, none of the mail on the server was appearing within the MS Outlook IMAP account settings.
The issue relates to a setting within Outlook. In order to correct, navigate into ‘Folder’ (ie; inbox)> ‘IMAP Folders’ > Un-tick the box that says ‘When Displaying hierarchy in Outlook’.
For more details, please refer to: http://answers.microsoft.com/en-us/office/forum/office_2013_release-outlook/outlook-2013-wont-receive-mail/4a466ea0-7d6b-43e6-9d05-a64857bc83f3?auth=1